W. B. HOOD, JR. AND J. C. NORMAN 
51 
branch. But we do try to make some assessment 
of the overall size and distribution, by inspect- 
ing the apex of the heart, of the left anterior de- 
scending coronary in the dog and in other ani- 
mals, to see whether this is an oversized or an 
undersized left anterior descending vessel. If it 
is undersized, we will move the occluding cuff 
up just below the septal artery to assure an ade- 
quate size infarct. 
J. C. Norman, Boston City Hospital, Boston, 
Mass.: In terms of tape, we've got about five 
hundred tapes in the lab; of baboons, cows, 
calves and dogs, I think the trustees of the hos- 
pital know that the dogs are there. They're not 
aware of the other animals. We've had a rather 
extensive experience in this particular area and 
in other areas; in terms of expensive instru- 
mentation, it can somehow disappear. The point 
I would like to make in this particular presenta- 
tion — and I'm sure Dr. Hood will have other 
comments — is that this is an old technique. We 
first developed it in terms of working on inter- 
mittent claudication as residents years ago. It 
opens up so very much in terms of gathering 
physiologic data on something that is clinically 
pertinent to us in the wards all the time. The 
conversations between Dr. Sawyer, Dr. La- 
Farge, and Dr. Garcia who runs the primate 
center and is present here, regarding the ques- 
tions of clinical relevancy has been simply a 
matter of moving back and forth from the In- 
tensive Care Unit down to the laboratory. We 
think that there is a great deal to be done yet. It 
is a relatively simple preparation. We, as Dr. 
Hood's animal caretakers and surgeons, can 
prepare the animals. He, of course, is the mind 
behind all this. Summing up: we enjoyed the 
work and hope to continue it for a long time. 
Chairman: Thank you Dr. Norman. Dr. 
Weber? 
Dr. K. T. Weber, Jr., University of Ala- 
bama, Birmingham Medical Center, Birming- 
ham, Alabama: We had some experience with 
calves, using vascular occluders and I'd like to 
echo the comment about the 100% mortality 
with fatal ventricular arrhythmias. However, 
we were recently much encouraged by the use of 
massive doses of regular insulin which were not 
only able to control the frequency of PVCs, but 
when injected locally into the coronary vessels 
distal from the ligation, was actually able to re- 
verse the ventricular tachycardia. We do not 
know the mechanism involved here and we're 
pursuing the problem at this point. I believe, 
however, that it might be of interest for those 
who are working with calves and possibly for 
those working with dogs. 
Dr. Norman: I've wondered if this fact 
about VF in the calf and pig might be related in 
some way to the relatively end-artery structure 
of the calf and pig, as compared to the dog. 
Your observations on the use of insulin are in- 
teresting. Do you give potassium glucose with 
this? 
Dr. Weber: Yes sir, we do. We give 10% 
glucose and intravenous potassium to prophy- 
lactically prevent complications. We thought 
that Hyatt possibly reported the same observa- 
tion in dogs last year in cardiovascular research 
and postulated the mechanism of epinephrine 
blockade. We were unable to block epinephrine, 
glucagon, or isoproteronal effects, inotropic or 
chronotropic, with massive doses of insulin. We 
believe at this point that it may be a metabolic 
effect, stabilizing membranes, preventing elec- 
tric chemical gradients and the like. We are not 
sure. 
Chairman : Again, I'd like to refer to the ar- 
icle by Alexander Leaf at Massachusetts Gen- 
eral, discussing ischemic changes: he referred 
to them in an article which, unfortunately, I 
can't cite for you. The study involved rabbits. 
The changes we were discussing earlier, in 
terms of opening pressure, revascularization or 
better vascularization of what's already there, 
were stimulated by the use of either glucose or 
glucose-insulin combinations. The presence of 
the insulin was not the critical factor. The 
changes were also stimulated by hyperosmolar 
concentrations of mannitol. What this was 
really was a study in cerebral ischemia, the im- 
provement and maintenance of circulation in 
the brain and profusion of the brain were 
markedly improved both by glucose, by mannitol, 
by prophylactic carbon dioxide infusion and by 
a combination of all three. Accordingly, there 
certainly is a substrate effect, probably from 
the glucose, and a hyperosmolar effect from 
substances like mannitol. 
